A group of people, some regular MUNI riders and some visitors, waited for a bus on Van Ness Avenue Monday June 2, 2014. Massive delays on the MUNI system in San Francisco, Calif. resulted when many drivers called in sick to protest a labor contract problem.

At Polk and Clay streets a crowd waited for their bus Monday June 2, 2014. Massive delays on the MUNI system in San Francisco, Calif. resulted when many drivers called in sick to protest a labor contract problem.

MTA workers steered disappointed cable car riders at Powell Street to a bus system after the cable car line was shut down Monday June 2, 2014. Massive delays on the MUNI system in San Francisco, Calif. resulted when many drivers called in sick to protest a labor contract problem.

Herman Morales (center) with the MTA steered disappointed cable car riders to a bus near the Powell Street station Monday June 2, 2014. Massive delays on the MUNI system in San Francisco, Calif. resulted when many drivers called in sick to protest a labor contract problem.

At Polk and Clay streets, bus riders waited patiently for a bus Monday June 2, 2014. Massive delays on the MUNI system in San Francisco, Calif. resulted when many drivers called in sick to protest a labor contract problem.

Visitors studied maps to try and find an alternative to the delayed street car service Monday June 2, 2014. Massive delays on the MUNI system in San Francisco, Calif. resulted when many drivers called in sick to protest a labor contract problem.

Visitors studied maps to try and find an alternative to the delayed...

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A man tried to enter a Market Street trolley that was too crowded Monday June 2, 2014. Massive delays on the MUNI system in San Francisco, Calif. resulted when many drivers called in sick to protest a labor contract problem.

At Market and Fifth Streets, street car riders lined up Monday June 2, 2014. Massive delays on the MUNI system in San Francisco, Calif. resulted when many drivers called in sick to protest a labor contract problem.

Cable car service was suspended Monday morning due to a sickout by San Francisco MUNI workers.

Photo: The Chronicle / Evan Sernoffsky

Cable car service was suspended Monday morning due to a sickout by...

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Riders crowd onto a San Francisco MUNI bus this morning.

Photo: The Chronicle / Evan Sernoffsky

Riders crowd onto a San Francisco MUNI bus this morning.

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A sign at a bus stop warns riders of potential large delays on San Francisco MUNI buses Monday morning due to a sickout by MUNI workers.

Photo: The Chronicle / Evan Sernoffsky

A sign at a bus stop warns riders of potential large delays on San...

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A share-ride bicycle stop on Market Street has only a few bicycles available.

Photo: The Chronicle / Evan Sernoffsky

A share-ride bicycle stop on Market Street has only a few bicycles...

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MTA workers directed people to a bus service at the end of the California Street cable car line Monday June 2, 2014. Massive delays on the MUNI system in San Francisco, Calif. resulted when many drivers called in sick to protest a labor contract problem.

As San Francisco commuters slogged their way home Monday on a transit system hobbled by the unscheduled absences of most of its operators, city transportation officials moved to stop the apparent sickout from moving into a second day. A memo e-mailed to employees and posted in yards warned workers who had called in sick that they will need doctors' notes to get paid.

"Operators claiming to be sick today, or in connection with any future 'sickout,' will be required to submit adequate verification from their health care provider in order to be eligible to receive paid sick leave," said a memo from Alicia John-Baptiste, the Municipal Transportation Agency's chief of staff.

Muni did not provide specific figures on the number of operators who called in sick for their scheduled Monday shifts, but MTA spokesman Paul Rose said 400 of the 600 Muni vehicles normally on the streets were not in service during both the morning and evening commutes.

It was not clear Monday evening whether the protest, which was not officially organized or sanctioned by the operators union, Transport Workers Local 250-A, would continue into a second day. Rose said Muni wasn't likely to know until early Tuesday.

During the evening commute, Muni deployed most of its depleted fleet downtown in an effort to clear out the busy Market Street corridor, where typically crowded stops, buses and rail cars were overwhelmed with frustrated commuters both in the subway and above ground.

Some riders reported waiting more than an hour for a bus to show up, which Rose warned was possible on all lines. Others climbed on their bikes and pedaled to work in more-crowded-than-usual bike lanes on Market Street and other thoroughfares. Taxis and ride services also saw a surge in business, according to informal reports. And disappointed tourists wondered why the cable cars weren't running.

Displeasure over proposal

The sickout came amid displeasure over a proposed labor agreement that was the subject of a vote Friday by Muni operators. The outcome of the vote has not been announced, but a handful of drivers who would not identify themselves at a news conference Monday afternoon said it was defeated.

Officials with Local 250-A did not take a position on the tentative agreement, which was reached with the assistance of a mediator, but called the MTA's offer unfair and unreasonable.

Under the proposal, Muni workers would get 11.25 percent in raises over two years, but they would pick up a 7.5 percent pension payment now paid by the MTA. The contract would push operator pay to about $32 an hour July 1, making Muni drivers the second-highest-paid transit workers in the country, according to the MTA.

Muni workers, like all San Francisco city employees, are prohibited from striking. Under a law approved by voters in 2010, if the union rejects the contract, the two sides go before an arbitrator who cannot rule against Muni management's proposals unless the union proves its interests outweigh "the public interest in efficient and reliable transit."

Union officials have complained that the standard is too high. In a statement on the union's website last week, Local 250-A President Eric Williams called the arbitration procedure "a lopsided and unfair process. The membership must take a stand, which will be communicated through your vote."

At a news conference Monday afternoon in front of MTA headquarters on South Van Ness Avenue, labor activist Steve Zeltzer said he was authorized to speak for the operators. He said the sickout was a driver-led rebellion against a contract that he said would result in pay cuts for operators in one of the nation's costliest cities.

"The drivers are sick," he said. "They're sick of the attacks, sick of being blamed for Muni's problems."

Grassroots strategy

A handful of drivers who wouldn't give their names out of fear of being fired said the sickout was a grassroots strategy that spread among transit operators by word of mouth and was kept largely confidential. Muni officials said they had heard rumors and anticipated some impact, especially as an increased number of operators called in sick Sunday evening.

"There were rumors," Rose said. "But nothing on the scale of what happened" Monday.

The scale of the sickout became evident early Monday, and the MTA put out an initial warning to riders shortly before 5 a.m. A tweet at 4:42 a.m. advised riders to "expect major delays on Muni today. Working to balance service the best we can across the city. Apologies for this inconvenience."

To help deal with the drastically reduced service, Muni had all express and limited buses stop at every stop. Cable car service was halted, and BART was honoring Muni fares in San Francisco and Daly City.

Muni officials struggled to maintain service, but commuters expressed frustration over the inevitable disruption many endured.

Squeezed onto a narrow concrete median at Fourth and Market streets, Junior Vaa, 28, said he had been waiting nearly an hour for the 9-San Bruno bus to head back to his home in Hunters Point.

"It's not fair, and they should already know that," he said. "Downtown is busy. People have to go to work. If you're taking the day off on this kind of job, maybe they should find somebody else who can do the work."

Emiko Tada was with a group of seven others visiting from Japan. They had planned to take a cable car from Powell Street.

"It's a pity, very sad. We wanted to get on," she said. They took a shuttle bus instead.

Drawing riders' ire

While the sickout clearly demonstrated the importance of Muni operators, many riders who endured long waits and overcrowded trains had little sympathy.

It took Kayla My, 15, an hour to get downtown from her home near Lowell High School so she could drop off papers for a new job. That was nearly twice as long as usual, she said. As she waited for an L-Taraval train at Powell Street Station, she estimated it would take at least another hour to get home.

"And we'll be packed in like sardines," Kayla said. "I'm a little bit annoyed. They can do their own thing to get what they want, but it's selfish. There are so many people who depend on them every day."

Some riders, like Yosimar Reyes, 25, said they supported the workers' struggle for a better contract.

"Even though it's troublesome for us, it's important that we look at how we can address the needs of the workers. Especially now, we can see how much they contribute to running this city."

But that wasn't going to get him to his home near Ocean Beach any quicker.